While many authors aren't fond of formal outlines, generally it's a good idea to decide how and when the story eventually ends. This does two things, first it eliminates the endless progression of chapters where little changes in the story, often leaving the story floundering for an ending. Secondly, it provides you with something to aim towards. Thus, as you write, each story element should eventually lead to the conclusion, and you'll flavor the writing towards that conclusion.
The story description is also useful, because it's essentially a one or two paragraph 'elevator speech' summarizing the story's conflicts. By writing that upfront, and keeping it in front of you, it's a constant reminded of the central conflicts driving the story. While various story elements will drift in various direction, the description will keep you on track, reminding you what to focus on.
Once you have those, you generally don't need a formal outline. One sign that you have a successful story idea is when it takes on a life of its own. Essentially, at some point the characters simply take over the story, acting on their own, at which point you simply sit back and try to record everything they say before they move on to the next encounter. When it happens, it's an exhilarating experience, and since your characters generally know the story (and their personalities) better than you, the author, does, it's best to forgo a chapter outline at that point.
Finally, most authors churn for some time, trying to get into any story, but it's mostly a problem of finding the right story. One you find a story that appeals to you, everything else basically falls into place. Thus, if you haven't found it yet, you may just be fishing in the wrong pond. If you're struggling to find a stroke story that captivates you, expand your range. Try something more detailed (i.e. more of an engaging plot with interesting characters). If you're trying for romance, try an action adventure or sci-fi saga. Again, you'll likely try several ideas before you hit the right one, but once you find what motivates You, you won't have the same problems in the future, as you'll know where to focus in the future. On a similar track, if the story doesn't take off after several chapters (i.e. if it's a struggle to type out a given chapter), then you're generally on the wrong track. Either the story doesn't appeal to you, or you're attacking it from the wrong direction (i.e. the characters refuse to act if those actions contradict their basic personalities).
Keep trying, you'll find that one magic story, and soon you'll be surfing on that one wave for a long time.